The present invention relates generally to voltage switches. More particularly, the present invention relates to an apparatus to provide novel bi-voltage level switching.
A back-to-back voltage switch is a device that switches between two different input voltages to produce an output voltage. Back-to-back voltage switches are used in high voltage circuit environments where initialization devices in a voltage pump need high voltage input to initialize the internal pump nodes. Back-to-back switches are also used in circuit applications that require switching between two different voltages, where one voltage needs to be isolated from the other voltage.
Prior art uses two back-to-back switches to accomplish voltage switching between two different voltages. The back-to-back switches used by prior art consists of four level shifter, four NMOS transistors and four PMOS transistors coupled together.
A problem with this approach is that a large amount of Read-While-Write (RWW) products used in the market today require simple layouts with minimal circuitry. Prior art methods for voltage switching include complex circuits with several electronic components that occupy a large amount of layout space.
Another problem with using a four level shifter is that level shifter contain significant internal resistance drops. A voltage signal passing through the prior art device using four level shifter is subject to several voltage potential losses due to these internal resistance drops. Thus the voltage signal becomes weak, inefficient, and looses its power. Power and efficiency loss in a voltage signal result in a low performance circuit.